As I was reading the first few pages of Trouble in Toadpool, the third of Anne Fine's wickedly funny books about the Mountfield family, a line from the film Gladiator suddenly popped into my head: "At my signal, unleash hell," growls Russell Crowe's über-tough guy Maximus. But even he and his fellow gladiators would blanch at the chaos unleashed by the Mountfields as they merrily demolish any fond illusions we might have about family life.

The first two titles in the series – The More the Merrier and Eating Things on Sticks – anatomised The Family Christmas and The Family Holiday, revealing those hallowed institutions to be nothing more than nightmares of grumpiness and bad feeling. Now it's the turn of The Annual Summer Fête – the kind of event that features stalls and entertainments, fortune telling and raffles, all of them clearly opportunities for rows and betrayals – to get a good kicking.

The dramatis personae are much the same – Mum and Dad Mountfield, their sons Harry and Ralph, their appalling Great Granny, bossy Aunt Susan and her lisping, wannabe-star daughter Titania, and practical joker Uncle Tristram. The plot is simple: Aunt Susan browbeats her family into helping her put on "The Great Toadpool Show", hoping to ingratiate herself with the local politburo, aka The Toadpool Ladies' Charity Guild, but forgetting that her relatives are only capable of generating mayhem.

Misunderstandings pile on mistakes, and conspiracies spiral out of control. Ralph finds himself committed to performing a trapeze act and spends most of his time trying to get out of it, while sibling rivalry breaks out among the adults. Great-Granny is a taciturn, malevolent figure, a cross between a golem and a troll, who comes into her own when given control of the Lucky Dip, where she scares off all customers.

Things work out, of course, but not in the way you might have expected – which is all part of the fun in a comedy of this sort. Anne Fine is the kind of writer who creates great characters and puts them through their paces in scenes constructed so well you can't see the joins. She's also a keen observer of human nature – "peeling back the nice surface of family life to show what's underneath", as it says on her website. Some of her other work is very dark, but for all its chaos Trouble in Toadpool feels rather sunny.

That's mostly to do with Ralph. We discover that he feels guilty about spoiling things for his cousin Titania in a previous story, and tries to make it up to her – without admitting anything. Cheerfulness keeps bursting in, with Kate Aldous's sparky black-and-white illustrations adding another layer of chirpiness. And although we might have to accept that hell is other people, particularly those we're related to, the lesson is that most of us muddle through, and put up with our nearest and dearest, however awful they are.

I do have one quibble – I thought the whole putting-on-a-show-at-the-fête set-up just the teensiest bit contrived, and was a little too much of an Aunt Sally in comparison to the series' other targets. Which probably means I won't be getting an invitation to take part in a family event at Fine Towers any time soon. But since she also says on her website "I'm always surprised murder in the domestic setting isn't more common," that's probably not a bad thing.